System on a Chip (SOC)

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“System on a Chip”, or SOC, refers to the integration of all the necessary electronic circuits of diverse functions onto a single chip, to come up with a complete electronic system that performs the more complex but more useful final product function. Thus, instead of building an electronic product by assembling various chips and components on a circuit board, SOC technology will allow all of these parts to be fabricated together on a single chip, which can function as the final product itself.

For instance, an SOC for electronic control of an automobile's suspension system will have the following distinct parts: 1) an accelerometer for detecting the car's motion; 2) an ADC for converting the accelerometer's analog output into digital data; 3) a digital signal processor for analyzing the digital data; 4) and an output driver system for controlling the mechanical behavior of the suspension system. In an SOC, all of these functionally individual circuits will be contained on a single integrated circuit.

System-on-a-Chip (SOC) must not be confused with System-in-a-Package (SIP), which is a device that consists of multiple individually fabricated chips that make up a complete electronic system housed in a single package. Thus, SIP pertains to an advanced type of packaging technology, while SOC deals with microchip fabrication technology.

The advantages offered by SOC technology include: 1) higher performance, since all the circuits will be on a single chip; 2) smaller space requirements; 3) lower memory requirements; 4) higher system reliability; and 5) lower consumer costs.

The challenges posed by SOC technology include: 1) larger design space; 2) higher design and prototyping costs; 3) longer design and prototyping cycle time; 4) more complex debugging; 5) lower IC yields and higher wafer fab costs due to the relatively larger die sizes involved; 6) integration of intellectual property from multiple (and possibly independent) sources.

Figure 1. An acoustic SOC from Akustica, Inc. composed of

microphones, support electronics, and software on a standard

CMOS chip; source: http://www.archive.chipcenter.com

Aside from these challenges, the task of electrically testing SOC's is daunting as well. Automatic testers today are built along specific specialty areas, and only the most expensive test systems cater to a wide variety of device technologies. An SOC, in essence being composed of many different devices, requires a test system that can perform electrical testing on all its analog and digital circuit components. SOC testing, therefore, generally requires high-end and consequently more expensive ATE systems.

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